Radio noises generated by automobiles have brought about a serious problem to communication equipments such as radios and TV. To cope with such a problem, some countries have established and enforced regulations for reducing such noises. It has been known that the ignition distributor for automobiles is one of the main points where such a noise is generated. When the spark occurs between the rotor electrode and each of the side electrodes, a jamming radio wave comes out. However no effective noise suppressing device for the distributor has been developed yet.